Electric connectors for nuclear fuel cartridges



March 30, 1965 J. LIERMANN 3,175,956

` ELECTRIC CONNECTORS FOR NUCLEAR FUEL CARTRIDGES Filed April 4, 1963 2Sheets-Sheet l @Wmms L, .f/M//// March 30, 1965 J. LIERMANN 3,175,956

ELECTRIC CONNECTORS ECR NUCLEAR FUEL CARTRIDGES Filed April 4, 1955 2sheets-sheet 2 United States Patent Oli ice 3,175,956 Patented Mar. 30,1965 3,175,956 ELECTRIC CONNECTORS FOR NUCLEAR FUEL CARTRIDGES JeanLiermann, Paris, France, assignor to Commissariat IEnergie Atomique,Paris, France Filed Apr. 4, 1963, Ser. No. 270,676 Claims priority,application France, Apr. 10, 1962, 893,925 2 Claims. (Cl. 176-77) Thepresent invention relates to a device for transmitting an electricpotential difference from one nuclear fuel cartridge to the next whenthese two cartridges are in contact by their ends and approximatelyaligned.

It is applicable more especially to the transmission along a stack ofcartridges of a potential diiference corresponding to a measurement, forexample a temperature measurement obtained by means of a thermoelectricprobe.

It is known to use for this application devices in which two contactstuds insulated from one another are disposed at each of the ends of thecartridges. When the ends of two approximately aligned successivecartridges are in contact, the opposed studs create between them anelectric connection. The geometric form of these studs is then such thatno accidental electric connection can occur between two contacts whichare not of like polarity. In one cartridge of the stack, the contacts ofone end are connected to the terminals of the thermoelectric probe. Ineach of the other cartridges, the contacts provided on one of the endsare connected to the contacts of like nature at the other end, thecartridges thus equipped transmitting the voltage step-by-step along thestack.

Known devices of this type include notably those in which each cartridgeend is provided with a central contact stud (of which the axis isidentical with that of the cartridge) and With an annular studconcentric with the first and electrically insulated therefrom. When twosuccessive cartridges are disposed end to end so as to bear one againstthe other, the central studs and the opposed peripheral studs,respectively, set up the necessary electric connections. However, thesearrangements have a number of disadvantages. More especially, theyrequire fairly considerable changes in the structure of the plugs bywhich the ends of the cartridges are closed, since their adoptioninvolves a considerable increase in the length of the cartridges, whichresults in certain modifications in the very operation of the reactorand throughout the subsequent course of treatment of the fuel.

In order to obviate these disadvantages, the invention resides mainly indisposing on the end plug of each cartridge a fixed central contact studand a peripheral stud supported by the upper edge of a resilient annularcup, which is slightly curved and substantially equal in diameter to theplug, the said cup being ixed to the plug concentrically with thecentral stud, in such manner that in the absence of stress theperipheral stud projects beyond the apparent contour of lthe remainderof the cartridge.

Among the advantages of the proposed arrangement, it is to be noted thatit makes it possible to equip existing cartridges without substantialmodication to the length of these cartridges. Moreover, owing to the useof a resilient cup of relatively large dimensions, it is possible tosubject it only to relatively low stresses as compared with thoseapplied to helical or spiral springs, for example, which are capable ofundergoing the deformations in the longitudinal direction of thecartridge which are necessary for establishing two electric contacts.

It will be apparent that the cartridges in contact at their ends must besubstantially aligned in order to ensure correct operation of such adevice. This algnment may be automatically brought about with somegeometrical forms of the cartridges and of the channel, while in othercases auxiliary elements may be provided to ensure alignment, whichmight be defective in the absence of such auxiliary elements. It isessential that these auxiliary elements should be such that the centralportion of the plug of the fuel element, of which the device accordingto the invention is fitted, is left entirely free. There may withadvantage be employed for correcting defective centering of thecartridges in relation to one another the device described in copendingUnited States patent application Serial No. 268,395, iled March 27,1963, also in the name of Commissariat a lEnergie Atomique.

Further advantages and features of the invention will be more readilyapparent from the following description of an embodiment, which is givenonly by way of indication and has no limiting character.

In the accompanying drawings:

FIGURE 1 is a vertical sectional View of a nuclear reactor channel,Within which is stacked a set of fuel cartridges.

FIGURE 2 is a sectional view to a larger scale illustrating the detailsof the construction of the contact device according to the invention.

FIGURE 3 is a view from above of a fuel cartridge.

It should first of all be mentioned that the principle of themeasurement of the temperature of a cartridge is applicable only if itis possible to use a thermoelect'ric probe of small dimensions which canbe introduced into or secured to the very thin walls of the cartridgewithout any danger of breakage of the canning of the cartridge. Such aprobe generally requires leading-out wires of very sroall diameter andit is diiicult to connect these to appropriate conductors which arecapable of passing through a sealing system to the outside of theenclosed space of the reactor for an appropriate utilisation of themeasurement. The particular conditions due to the circulation of thecooling iluid and to the effect of radiation during operation areincompatible with a simple connection of the wires of the probe to thesaid conductors. It is necessary to provide various systems, which aregenerally complex and diiiicult to produce with members of simple formwhich consist of materials capable of behaving correctly in the presenceof the neutron liux.

The device according to the invention permits obviating the aforesaiddisadvantages while aiording particularly appreciable reliability ofoperation.

In FIGURE 1, there is illustrated by way of example a nuclear reactorchannel extending through the moderator structure 2 of the reactor. Ofcourse, the invention could be applied in the same way in other reactortypes, and notably in cases where the cartridges are stacked inside atube in a reactor channel. The upper portion 3 of the channel, which isclosed by a iluid-tight plug 4, extends, between the moderator structure2 and the protective shield 5, through a free space 6 through which thecooling liquid circulating within the channel 1 can escape after havingpassed through apertures such as 7. Stacked in the channel underconsideration is a number of cartridges such as 8 constituting what isconventionally called a train of cartridges. The end of this traincomprises a false cartridge 9, i.e. an element having the samedimensions and geometrical characteristics as the cartridges 8, butcontaining no issile material.

The fuel cartridges comprise at each of their ends 10 Contact membersdesigned in accordance with the invention, of which the constructionaldetails will hereinafter be explained. One of the cartridges within thetrain, for example the cartridge 8a, is provided with a thermoelectricprobe 11 secured to its canning, the leading-out wires of which probeare connected to a microcasing 12 fast with the body of the cartridge.The said microcasing is in turn connected to the Contact memberssupported by that end of the cartridge Sawhich is closer to the outletof the channel, by means of two conductors such as 13. Each of the othercartridges 8 situated between the cartridge 8a and the outlet of thechannel (in the figure, only one cartridge of this type and the falsecartridge 9 are shown) comprises conductors 14 which provide theconnection between the respective contact members mounted on each oftheir ends. The outlet plug 4 is provided with a fluidtight passage 15for leading-out the connecting wires which, when connected to anappropriate measuring instrument, supply an exact reading of the voltageset up across the terminals of the thermoelectric probe 11.

FIGURE 2 shows in greater detail the ends of two successive cartridgeswithin a channel and illustrates the particular construction of thecontact members mounted respectively on each of the said cartridges. Thelatter, which are identical to one another, each comprise a canningterminated at both ends by plugs such as 21 which seal the canning influid-tight fashion with the aid of continuous weld beads 22. Rigidlysecured to each of the plugs by means of screws or rivets such as 23 isa metal support 24. The Contact device proper comprises a central stud25 secured along the axis of the cartridge by a screw 26 to the support24 and a peripheral stud 27 secured by means of rivets such as 29 to aflexible cup 28 coaxially maintained around the stud 2S and bearingagainst the support 24 by means of a tubular casing 30 screwed on to thelatter. Two ceramic cross-members or spacing members 31 and 32 provideappropriate electric insulation between the two studs 2S and 27 on theone hand and the studs and the canning on the other hand.

Each of the two aforesaid contact elements is connected by conductors 33and 34 (33 in the case of the central stud and 34 in the case of theperipheral stud) respectively, either to studs of like nature secured tothe opposite end of the cartridge, or to positive and negative elementsof the thermoelectric probe through a microcasing, in the mannerdescribed with reference to FIGURE l.

The conductors 33 and 34 are disposed within insulating sheathings suchas 35 maintained in contact with a longitudinal supporting lug 36 xedlymounted between the fins 37 of the canning 20 by any appropriate means,notably by welding. The sheathings 35 are aligned along the lug 36 bygrooved guides 38 (FIGURE 3) situated at regular intervals along itslength.

It will also be seen from FIGURE 2 that the aforesaid cartridges areprovided at each of their ends with annular male and female membersWhose function is on the one hand to ensure centering of one cartridgein relation to the next along the train of cartridges, and on the otherhand to permit satisfactory contact between the studs of two successivecartridges, while preserving the weld of the conductor wires on thestuds. These centering members, which are described in greater detail inthe copending United States patent application already mentioned in theforegoing, are denoted by the references 39 for the male member and 40for the female member in FIGURE 2. They are iixedly mounted on the endsof the cartridges and are so formed as to afford, when the cartridgeshave been positioned, a suicient lateral clearance to determine theclosest possible Contact between the studs of like nature from onecartridge to the next. Extending through the elements 39 and 40 areducts 41 and 42 for the passage of the cables 35, in which are disposedthe connecting conductors 33 and 34.

In addition to the advantages already mentioned, it will be seen thedevice according to the invention makes it possible to transmit veryreliably the items of information received from the thermoelectricprobe, even if the alignment of the various cartridges is not perfect.Moreover, although the resilience of the cup 28 constantly ensuresappropriate contact between the successive peripheral studs Y 27, thecontact between the central studs 25 may also be further improved byforming them with a male profile and a female profile respectively whichcan slide one with respect to the other regardless of the relativedisalignment of the cartridges.

It is also to be noted that the device according to the inventionutilises as resilient element a cup having considerable radialdevelopment and small thickness. The stresses which are set upin the cupfor a given longitudinal deformation are consequently much smaller thanin the helical or spiral return spring which would have to be providedin association with, for example, a movable central stud. Theconsequences of the changes in the mechanical characteristics due toneutron irradiation are therefore much less serious.

Of course, the invention is in no way limited to the embodiments whichhave been described by way of example in the foregoing, but covers allvariants thereof.

I claim:

1. A plurality of nuclear reactor fuel cartridges stacked end-to-end ina nuclear reactor channel the ends of the cartridges being closed byplugs and adjacent plugs having co-operating annular male and femalealigning members respectively, a rigid support secured to each end ofeach of said plugs, a central electric contact stud secured to saidsupport, a peripheral electric contact stud surrounding said centralstud, a resilient cup supporting said peripheral stud and mounted on andelectrically insulated from said support, means for electricallyinsulating said studs from each other, said peripheral stud normallyextending beyond said central stud and sheathed electric conductorsextending through said aligning members and connecting like studs foreach fuel cartridge, said aligning members surrounding said studs.

2. Fuel cartridges as described in claim 1, including a thermo-electricprobe secured to one of said cartridges, terminals for said probe, amicro-casing connecting said terminals andrsaid conductors for saidcartridge, a longitudinal securing lug on each of said cartridges andguides on said lugs for aligning said conductors.

References Cited by the Examiner UNITED STATES PATENTS 3,104,215 9/ 63Guneratne 176-79 FOREIGN PATENTS 226,454 1/ 60 Australia 176-79 614,2792/61 Canada 176-68 1,252,173 12/60 France 176-19 875,462 8/61 GreatBritain 176-77 CARL D. QUARFORTH, Primary Examiner.

1. A PLURALITY OF NUCLEAR REACTOR FUEL CARTRIDGES STACKED END-TO-END INA NUCLEAR REACTOR CHANNEL THE ENDS OF THE CARTRIDGES BEING CLOSED BYPLUGS AND ADJACENT PLUGS HAVING CO-OPERATING ANNULAR MALE AND FEMALEALIGNING MEMBERS RESPECTIVELY, A RIGID SUPPORT SECURED TO EACH END OFEACH OF SAID PLUGS, A CENTRAL ELECTRIC CONTACT STUD SECURED TO SAIDSUPPORT, A PERIPHERAL ELECTRIC CONTACT STUD SURROUNDING SAID CENTRALSTUD, A RESILIENT CUP SUPPORTING SAID PERIPHERAL STUD AND MOUNTED ON ANDELECTRICALLY INSULATED FROM SAID SUPPORT, MEANS FOR ELECTRICALLYINSULATING SAID STUDS FROM EACH OTHER, SAID PERIPHERAL STUD NORMALLYEXTENDING BEYOND SAID CENTRAL STUD AND SHEATHED ELECTRIC CONDUCTORSEXTENDING THROUGH SAID ALIGNING MEMBERS AND CONNECTING LIKE STUDS FOREACH FUEL CARTRIDGE, SAID ALIGNING MEMBERS SURROUNDING SAID STUDS.